Non-contact type switches are commonly used in a wide variety of applications. For example, non-contact type switches are commonly used in interlock systems that restrict access to certain areas or equipment. For example, in an industrial setting, a potentially hazardous robot may be surrounded by a barrier that has an entrance gate. The gate may be equipped with a non-contact type switch whose state depends on whether the gate is open or closed. If the non-contact type switch indicates an open gate, a controller may command the robot to enter a safe state, such as a non-moving state.
In some instances, non-contact type switches may be willfully defeated in order to bypass certain safety or other features provided by the non-contact type switches. For example, if a non-contact type switch on one side of a gate is operated by a magnetic relay, the operator may permanently attach a magnet to the relay, thereby permanently closing the relay even when the gate is opened. What would be desirable, therefore, is a more secure non-contact type switch that would be more difficult to defeat. Such a non-contact type switch would have a wide variety of applications, including many interlock applications.